1. Field of the Invention
The present invention relates to a method of promoting the reproductive performance of penaeus shrimps, particularly to a method of promoting the reproductive performance of female penaeus shrimps.
2. Description of the Related Art
Since 1970s, due to the fast development of propagation techniques brings about the great achievement of aquaculture in Taiwan, especially in marine shrimps farming. The aquaculture of marine shrimps plays an important role in the fisheries in Taiwan. Currently, the main farming species of shrimp in Taiwan are mainly based on penaeus shrimps, which are bigger in size, rapid developing and easy for culturing.
The farming of penaeus shrimps in Taiwan have first achieved in 1968, following by a large number of commercial hatchery setting up among everywhere to supply high quantity of shrimps to the industry. However, the farm-raised production of penaeus shrimps in Taiwan has been collapsing since 1988, mainly caused by poor management of ecology and viral infection, such as WSSV (white spot syndrome virus), TSV (Taura syndrome virus) and YHV (yellow head virus). Therefore a significant amount of farming shrimps die from diseases, and accordingly the shrimp farming in Taiwan has no longer flourished anymore.
In general, the shrimp aquaculture in Taiwan is highly depended on wild shrimp broodstocks, which are commonly hatched in tanks for growing to maturity, sequentially treated of unilaterally eyestalk-ablation and fed fresh diets. As following, the ovarian development and reproductive performance of hatched wild shrimps will be observed. However, most wild shrimps are pathogen-positive or poor in immunity and physical quality, which may be more susceptible to some pathogen infection. In this situation, it is risky to adopt the wild shrimp broodstocks using for industrial reproduction in aquaculture. On the other hand, for moderating the disease problems of farming shrimps, specific pathogen-free (SPF) broodstocks are selected or widely imported from other countries. However, most SPF shrimps are still susceptible to pathogen infection especially after the unilaterally eyestalk-ablated treatment accompanying with physiological failure or serious death. Hence, whatever using expensive SPF broodstocks or wild catch-broodstocks, they are all ineffectual to avoid pathogen-infection problems in farming industry of shrimps in Taiwan. It seem that it is an urgent need to establish a strategy for aquaculture industry in order to obtain pathogen free shrimp broodstocks successfully.
Recently, for successfully restrict the infection of pathogen on farmed shrimps, some probiotics and immunostimulants are widely developed and applied on aquaculture diets, in order to improve the immunity and disease resistance of farmed-shrimps. The most popular immunostimulants used in aquaculture are polysaccharides which are widely extracted from the cell walls of bacterium, yeast and algae, glucan and alginic acid. In general, immunostimulants used in larvae and growth-out phases of aquatic shrimps have been shown to have good efficacy on pathogen resistance. However, for female broodstocks, unilaterally eyestalk-ablated female broodstocks particularly, it is lack of a sufficient immunostimulant involved in daily diets, for the sake of promoting the innate immunity, as well as the reproductive ability of shrimps. Therefore, it is necessary to establish a useful approach for penaeus shrimps not only can improve the health status of broodstock but also can increase the quality and production of larvae.